Student Essay on Electroplating

Electroplating

Summary:   Describes the process of electroplating. Explains how and why it is done. Explores the use of electroplating in the printing industry.

We have all seen chromium-plated auto-mobile bumpers, gold plated watches, and silver-plated spoons. Many other familiar things are given metal coating to make them look more attractive and to protect them from rust. These objects are usually made of steel, which is strong and cheap, and covered thinly with the other metal.

Other common way of coating an object with metal is called electroplating. An electric current is used to put the metal coating on the object and make it stick there.

To plate a spoon with silver, for example, the spoon is placed in a chemical solution that contains silver. The spoon is attached to the cathode, or negative terminal, of some source of electric current. A solid bar of silver id connected to the anode, or positive terminal, of the same electric circuit. An electric current is them passed through the spoon, the silver bar, and the solution.

Silver from the solution is drawn to the spoon and deposited on it. This gives the spoon a smooth, even plating of silver. While this is happening the silver bar is slowly dissolving into the solution. This silver replaces the silver that has been deposited on the spoon from the solution.

This is what happens during electroplating. How it happens is easy to understand if you know something about atoms and the way they behave.

Atoms are tiny particles that make up all matter. Every atom has a large central core called the nucleus. The nucleus is surrounded by much smaller particles called electrons, which spin around it much as the earth and the other planets spin around our sun.

Under certain conditions atoms can lose or gain electrons. This throws the atoms out of balance and gives them a positive or negative electric charge. Such electrically charged atoms are called ions. An ion that has been formed by an atom's losing electrons will try take on other electrons to regain its balance. When it takes on these electrons, it loses its electrical charge. Once again it becomes a neutral atom. When metal atoms become ions, they always lose electrons.

How are these laws of nature used in electroplating? When the spoon is connected to the cathode of the electronic circuit, it becomes loaded with extra electrons. Silver ions from the solution are attached to the spoon. When they reach it, they take on electrons, lose their charges, and settle firmly on the spoon's surface. Bit by bit a silver coating is built up.

At the same time, silver atoms on the silver anode bar are losing electrons. These atoms thus become ions. They pass into the solution and take the place of the ions that were deposited on the spoon.

In some electroplating processes the anode is not made of the metal that is being used for plating. Then all the metal for the plating must come out of the solution. When the metal ions in the solution are used up, new solution must be added.

Uses of electroplating

Adding beauty or protection are not the only uses of electroplating. Electroplating can also be used to build up worn machine parts by adding new metals. Electroplating done in reverse is called electropolishing. In this process the metal object is connected to the anode instead of the cathode, so that it loses a thin layer of metal instead of gaining one. This leaves a very smooth, bright surface and is cheaper than ordinary polishing.

Printed electric circuits for radios, television sets, and missiles are often protected by electroplating. Copper is deposited in a thin layer over a fiber base. The unwanted portions of the copper are then removed. This leaves a network of copper through which an electric current can flow.

A special type of electroplating called electroforming is used to reproduce delicate objects with many details. Printing plates and the master phonograph records from which copies are pressed are produced by electroforming.

The metal is deposited as a thick coating, or shell, over a model of the object that is to be reproduced. When the shell is separated from the model, it forms a perfect metal copy of the model in reverse.

Electroforming is very important in the printing industry. It has many uses, such as in making the plates that fine illustrations and books are printed from. Printers call it electrotyping.

Electroforming is also used for making parts out of very hard, metals that cannot be shaped by machine. Rocket exhaust nozzles can be made in this way.